Oral 1α-hydroxyprevitamin D in methods for increasing blood level of activated vitamin D

ABSTRACT

Method of increasing activated vitamin D blood level by administering orally a 1α-hydroxyprevitamin D. This previtamin D form increases vitamin D blood level without significant risk of hypercalcemia associated with other oral dosing of vitamin D forms. The 1α-hydroxyprevitamin is compounded into a pharmaceutical composition in combination with a pharmaceutically acceptable excipient.

This is a continuation of application Ser. No. 08/188,942, filed Jan.26, 1994, now U.S. Pat. No. 5,622,961 which is a file wrappercontinuation of application Ser. No. 07/901,886, filed Jun. 22, 1992,now abandoned.

TECHNICAL FIELD

This invention relates to a method for increasing the blood level ofactive vitamin D compounds. More specifically, the invention relates toorally administering the 1α-hydroxylated previtamin form of vitamin Dcompounds in order to increase the blood level of the correspondingactive vitamin D compound.

BACKGROUND OF THE INVENTION

Vitamin D is known to be important in the regulation of calciummetabolism in animals and man. See, Harrison's Principals of InternalMedicine: Part Eleven, "Disorders of Bone and Mineral Metabolism,"Chapter 335, E. Braunwald et al., (eds.), McGraw-Hill, New York (1987)pp. 1860-1865.

Vitamin D₃ is synthesized endogenously in the skin of animals and manfrom 7-dehydrocholesterol by an ultraviolet-mediated photochemicalreaction which breaks the B ring of the 7-dehydrocholesterol betweencarbon-4 and carbon-9 to form previtamin D₃. The triene previtamin D₃ isunstable and over time thermally converts to vitamin D₃. At normal bodytemperature an equilibrium exists between previtamin D₃ and vitamin D₃,as seen below. As vitamin D₃ is further metabolized in vivo thisequilibrium shifts to the vitamin D₃ form. ##STR1##

It is known that vitamin D₃ must be hydroxylated in the carbon-1 and thecarbon-25 position before it is activated, i.e., before it will producea biological response. A similar metabolism appears to be required toactivate the other forms of vitamin D, e.g., vitamin D₂ and vitamin D₄.As is generally understood and used herein, the term "vitamin D" isintended to include vitamins D₃, D₂, and D₄. The term "activated vitaminD," as used herein, is intended to refer to vitamin D which has beenhydroxylated in at least the carbon-1 position of the A ring, e.g.,1α-hydroxyvitamin D₃.

Functionally, vitamin D is more appropriately considered a hormone thana vitamin. When activated, vitamin D interacts with a vitamin D receptorprotein and this interaction ultimately results in some form ofbiological response. For example, 1α,25-dihydroxyvitamin D₃ is known tobe a potent stimulator of calcium absorption from the intestine, suchabsorption is mediated by the interaction of the 1α,25-dihydroxyvitaminD₃ molecule and the vitamin D receptor protein located in the epithelialcells (enterocytes) which line the intestine.

In recent years it has become evident that the vitamin D receptorprotein is widely distributed in the bodies of animals and man. Thus, itis not surprising that in addition to influencing calcium homeostasis,activated vitamin D has been implicated in osteogenesis, modulation ofimmune response, modulation of the process of insulin secretion by thepancreatic B cell, muscle cell function and the differentiation andgrowth of epidermal and hemopoietic tissues.

Such a wide range of biological actions suggests that the activatedforms of vitamin D compounds should be valuable therapeutic agents for awide range of maladies such as metabolic bone disease, osteoporosis,psoriasis, psoriatic arthritis, breast cancer and HIV infection.Unfortunately, when these agents are administered orally, the potentstimulation of calcium absorption by activated vitamin D can readilycause a dangerous hypercalcemia before the desired therapeutic responseis obtained. For this reason, the activated vitamin D compounds aregenerally considered to have a low therapeutic to toxic ratio or lowtherapeutic index. Additionally, the presently known oral formulationswhen administered produce an unphysiologically rapid increase in theblood level of both calcium and activated vitamin D hormone followed byan almost as rapid decrease in the blood level of activated vitamin Dhormone. Such rapid peaks and valleys of either the blood calcium or theactivated vitamin D hormone are undesirable and perhaps harmful.

Recognizing the great potential of activated vitamin D as a therapeuticagent, alternative routes of administration which would allow highersustained blood levels to be achieved and yet avoid the toxicityproblems presented by the oral dosage form have been sought. To thisend, an injectable form of 1α,25-dihydroxyvitamin D₃ has been developedby Abbott Laboratories and is marketed under the trade name Calcijex forthe management of hypocalcemia in patients undergoing chronic renaldialysis. Topical and transdermal forms of the drug have also beensuggested by Holick, U.S. Pat. No. 4,230,701.

These alternative routes of administration, however, lack theconvenience and the reliability of an oral dosage form and, to thatextent, have diminished the practicality and attractiveness of activatedvitamin D compounds as therapeutic agents. What is needed, is an oraldosage form which produces a more physiological sustained increase inthe blood level of activated vitamin D and has a more acceptabletherapeutic index than is presently possible with heretofore known oralformulations of activated vitamin D.

SUMMARY OF THE INVENTION

The present invention responds specifically to the long-felt needheretofore unmet by the prior art and especially with a view toovercoming the inherent inadequacies of oral vitamin D formulations. Thepresent invention provides a pharmaceutical composition and method forincreasing activated vitamin D blood level by administering orally acompound of formula (I) as defined hereinbelow. The compounds of formula(I) include 1α-hydroxyprevitamin D and 1α,25-dihydroxyprevitamin D.

In accordance with the invention, it has been unexpectedly found thatorally administered 1α,25-dihydroxyprevitamin D produces a sustainedincrease in the blood level of 1α,25-dihydroxyvitamin D and has a highertherapeutic index than does orally administered 1α,25-dihydroxyvitaminD. The increased activated vitamin D blood level is achieved withsignificantly less hypercalcemia than that resulting from oral dosing ofthe 1α,25-dihydroxyvitamin D.

The present invention is carried out by manufacturing1α-hydroxyprevitamin D so that the 1α-hydroxyprevitamin D form remainsrelatively stable at room temperature. The 1α-hydroxyprevitamin D isthen administered to an animal or human being in an oral dosageformulation. As the 1α-hydroxyprevitamin D is released from the oraldosage formulation, it is absorbed from the intestine into the blood. Inthe 1α-hydroxyprevitamin D form, the compound is inactive (i.e., doesnot bind to the vitamin D receptor protein) and does not stimulateintestinal calcium absorption. As the 1α-hydroxyprevitamin D is warmedby the core temperature of the animal or human being, it is thermallyconverted to the corresponding activated vitamin D, i.e., to its thermalisomer. The thermal conversion to the active form takes a sufficientlylong period of time such that most of this conversion occurs in the timeperiod after the 1α-hydroxyprevitamin D has been absorbed into the bloodstream of the animal or human being. Thus, the 1α-hydroxyprevitamin Doral dosage formulation produces a greater sustained blood level of thecorresponding activated vitamin D with significantly less stimulation ofintestinal calcium absorption than is obtained by administering orallythe corresponding activated vitamin D itself.

The foregoing and other advantages of the present invention are realizedin one aspect thereof in a method for increasing the blood level ofactivated vitamin D in an animal or human being by administering orallyan effective amount of 1α-hydroxyprevitamin D. A preferred embodiment of1α-hydroxyprevitamin D is 1α,25-dihydroxyprevitamin D₃.

In another aspect, the invention is a method of increasing blood levelof activated vitamin D for a sustained period of time, typically greaterthan four hours.

In yet another aspect, the invention is a method for treatingosteoporosis by administering orally an effective amount of1α-hydroxyprevitamin D. In a further aspect, the invention is a methodof treating psoriasis by orally administering an effective amount of1α-hydroxyprevitamin D.

The compounds of formula (I) are provided in pharmaceutical compositionsin combination with a pharmaceutically acceptable excipient. Thesecompositions constitute another aspect of the invention. Preferredcompositions include compounds of formula (I) which include1α,25-dihydroxyprevitamin D₃, 1α,25-dihydroxyprevitamin D₂, and1α,25-dihydroxyprevitamin D₄.

Other advantages and a fuller appreciation of the specific adaptations,compositional variations and chemical and physical attributes of thisinvention will be gained upon examination of the detailed descriptionand appended claims.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates broadly to therapeutic methods forameliorating certain medical conditions by improving blood levels ofactivated vitamin D, and specifically, to improving such levels byadministering an oral formulation with significantly less resultanthypercalcemia. These attributes are achieved through a novel treatmentof a subject with the compounds of formula (I), as defined hereinbelow.

In accordance with the invention, it has been found that whensubstantially pure 1α-hydroxyprevitamin D is administered orally, itproduces a greater sustained increase in the blood level of activatedvitamin D and significantly less hypercalcemia and hypercalciuria thanthe same amount of activated vitamin D administered orally in previouslyknown formulations. As used herein, the term "substantially pure" meansat least 85% pure 1α-hydroxyprevitamin D. The term "sustained" as usedherein means a blood level which remains relatively constant (i.e., ±10pg/ml) for a period greater than a defined period.

The 1α-hydroxyprevitamin D of the present invention has the generalformula (I): ##STR2## wherein R_(a) is a side chain having at least 7carbon atoms, and can be branched or unbranched, saturated orunsaturated, hetero-substituted or nonhetero-substituted, cyclic ornoncyclic and wherein the thermal isomer (i.e., vitamin form) of the1α-hydroxyprevitamin D of the general formula increases the serumcalcium of the vitamin D deficient rat as determined by standardtechniques used by biochemists in the vitamin D area.

Among the preferred 1α-hydroxyprevitamin D of the present invention arethose having the formula (II): ##STR3## wherein B and C are eitherhydrogen or a carbon to carbon bond forming a double bond between C22and C23; R₁, R₃, R₄ and R₅ are each independently hydrogen, hydroxy,lower alkyl, O-lower alkyl, O-lower acyl, O-aromatic acyl or flouro; andR₂ is hydrogen or lower alkyl. Most preferred among the compounds offormula (II), i.e., most preferred 1α-hydroxyprevitamin D compounds,are:

1α,25-dihydroxy-precholecalciferol [1α,25-(OH)₂ preD₃ ];

1α,24,25-trihydroxy-precholecalciferol [1α,24,25-(OH)₃ preD₃ ];

1α-hydroxy-precholecalciferol[1α-(OH)preD₃);

1α,24-dihydroxy-precholecalciferol[1α,24-(OH)₂ preD₃);

1α,24-dihydroxy-25-fluoro-precholecalciferol[1α,24-(OH)₂ 25FpreD₃ ];

1α,25-dihydroxy-preergocalciferol(1α,25-(OH)₂ preD₂ ];

1α,24,25-trihydroxy-preergocalciferol[1α,24,25-(OH)₃ preD₂ ];

1α-hydroxy-preergocalciferol [1α-(OH) preD₂ ];

1α,24-dihydroxy-preergocalciferol[1α,24-(OH)₂ preD₂ ];

1α,24-dihydroxy-25-fluoro-preergocalciferol[1α,24-(OH)₂ 25FpreD₂ ];

1α,25-dihydroxy-previtamin D₄ [1α,25-(OH)₂ preD₄ ];

1α,24,25-trihydroxy-previtamin D₄ [1α,24,25-(OH)₃ preD₄ ];

1α-hydroxy-previtamin D₄ [1α-(OH)preD₄ ];

1α,24-dihydroxy-previtamin D₄ [1α,24-(OH)₂ preD₄ ]; and

1α,24-dihydroxy-25-fluoro-previtamin D₄ 1α,24-(OH)₂ 25FpreD₄ ].

In the formulae shown in this specification and in the claims, a wavyline to substituent X indicates that the substituent can bestereoisomeric alternate forms. Wherever in this specification and inthe claims the word "lower" is used as a modifier of alkyl or acyl, itis intended to identify a hydrocarbon chain having from about 1 to 4carbon atoms which has either a straight chain or branched chainconfiguration. Specific examples of such hydrocarbon chains are: methyl,ethyl, propyl, butyl, isobutyl or t-butyl, and formyl, acetyl,propionyl, or butyryl. The term "aromatic acyl" as used herein and inthe claims is meant to identify a benzoyl group or a substituted benzoylgroup such as nitrobenzoyl or dinitrobenzoyl.

In a preferred embodiment, the compounds of formula (I) are provided ina crystalline form. 1α-Hydroxyprevitamin D in the crystalline formremains quite stable at room temperature with minimal conversion to the1α-hydroxyvitamin D form. The compounds of formula (I), i.e.,1α-hydroxyprevitamin D, can be readily manufactured in crystalline formaccording to the procedure described in Vandewalle, U.S. Pat. No.4,539,153.

The compounds of formula (I) are useful as active compounds inpharmaceutical compositions. Such compositions may includephysiologically acceptable excipients or vehicles. These pharmaceuticalcompositions constitute another aspect of the invention.

The pharmacologically active compounds of this invention can beprocessed in accordance with conventional methods of pharmacy to producemedicinal agents for administration to patients, e.g., mammals,including human beings. For example, dosage forms of the compounds offormula (I) with conventional excipients, include admixtures suitablefor oral administration. Dosage forms of the 1α-hydroxyprevitamin D canbe combined with any nontoxic pharmaceutically acceptable carrier, suchas cornstarch, lactose, or sucrose, which does not deleteriously reactwith the active compounds. The formulation can be produced in tablet,capsule, powders, troches and lozenges. Whatever method of formulationis used, care should be taken to avoid extended exposure to solvents andheat as under such conditions there will be a tendency for a portion1α-hydroxyprevitamin D to convert to the 1α-hydroxyvitamin D form.Because heat and dissolution are preferably avoided, the preferredmethod of tablet formulation is the method known as dry granulation.

The dosage forms may also contain adjuvants, such as preserving orstabilizing adjuvants. They may also contain other therapeuticallyvaluable substances or may contain more than one of the compoundsspecified herein and in the claims in admixture.

Advantageously, the compounds of the present invention or combinationsthereof with other therapeutic agents can be administered in dosageamounts of from 0.1 to 100 micrograms per day. In relation toosteoporosis, doses from about 0.5 to about 25 micrograms per day aregenerally effective. If the compounds of the present invention areadministered in combination with other therapeutic agents, theproportions of each of the compounds in the combination beingadministered will be dependent on the particular disease state beingaddressed. For example, in the case of osteoporosis, one may choose toadminister the previtamin form of an activated vitamin D compound withan estrogen compound, Calcitriol, Calcitonin or a bisphosphonate. Inpractice, higher doses of the compounds of the present invention areused where therapeutic treatment of a disease state is the desired end,while the lower doses are generally used for prophylactic purposes, itbeing understood that the specific dosage administered in any given casewill be adjusted in accordance with the specific compounds beingadministered, the disease to be treated, the condition of the subjectand the other relevant medical facts that may modify the activity of thedrug or the response of the subject, as is well known by those skilledin the art.

The 1α-hydroxyprevitamin D is administered to the animal or human inoral dosage formulation. As the 1α-hydroxyprevitamin D is released fromthe oral dosage formulation, it is absorbed from the intestine into theblood. 1α-Hydroxyprevitamin D does not interact with the vitamin Dreceptor protein of the enterocytes and, therefore, does not stimulateintestinal calcium absorption.

It is also known that the binding of activated vitamin D with thevitamin D protein receptor of the enterocyte induces the release ofenzymes which degrade a significant portion of the unbound activatedvitamin D present in the intestine. Such degradation decreases theamount of activated vitamin D available for absorption into the bloodstream. Since 1α-hydroxyprevitamin D does not bind with the vitamin Dreceptor protein there is no enzyme induction. Thus, less degradationoccurs in the intestine and a greater amount is available for absorptioninto the blood stream than is the case with the corresponding activatedvitamin D.

As the 1α-hydroxyprevitamin D is warmed by the core temperature of theanimal or human being, it is thermally converted to the correspondingactivated vitamin D. The reaction time for thermal conversion to theactive form is sufficiently long so that most of the conversion occursover time after the 1α-hydroxyprevitamin D has been absorbed into theblood stream. Thus, the 1α-hydroxyprevitamin D oral dosage formulationproduces a greater sustained blood level of the corresponding activatedvitamin D with significantly less stimulation of intestinal calciumabsorption than is possible with a comparable oral dosage amount of theactivated vitamin D itself.

The present invention is further explained by the following exampleswhich should not be construed by way of limiting the scope of thepresent invention. In the following examples, high pressure liquidchromatography (HPLC) was performed on a Waters Instrument, using aZorbox SilODS column.

EXAMPLE 1

Time course of 1α-hydroxyprevitamin D conversion to 1α-hydroxyvitamin D.

One and a half micrograms of 1α-hydroxyvitamin D₂ was dissolved in 2.00ml ethanol. This solution was then subjected to a 60° C. water bath for24 hours. Fractions of 1α-hydroxyprevitamin D₂ [1α-OH-pre-D₂ ] werecollected in nearly pure amounts from this treated sample. Theseprevitamin fractions were pooled in a single test tube, dried undernitrogen gas on ice and eventually redissolved in 1.00 ml ethanol. Thepooled fraction of previtamin, upon HPLC analysis, indicated 96% wasprevitamin at t=0 time.

A tube with the pooled previtamin was then placed in a 37° C. waterbath. 50 μl aliquots were removed and placed into LVI tubes with a coldwater jacket around them. Samples were chromatographed to determine thepercent of 1α-hydroxyprevitamin D₂ and 1α-OH-D₂ present in each sample.Sampling times were 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 6.0, and8.0 hours. Results are presented below in Tables 1 and 2:

                  TABLE 1                                                         ______________________________________                                        1α-OH-D.sub.2 SAMPLE PREPARATION                                          SAMPLE           % PREVITAMIN                                                                              % 1α-OH-D.sub.2                          ______________________________________                                        Starting Material                                                                            0.00        99                                                   24 hours at 60° C. 8 92                                                Pooled Fractions 96  4                                                      ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        TIME COURSE OF 1α-OH PREVITAMIN D.sub.2                                   SAMPLE                                                                        (T = hrs) % 1α-OH-PRE-D.sub.2 % 1α-OH-D.sub.2                   ______________________________________                                        T = 0.0      96            4                                                    T = 0.5 93  7                                                                 T = 1.0 90 10                                                                 T = 1.5 86 13                                                                 T = 2.0 83 17                                                                 T = 2.5 79 21                                                                 T = 3.0 77 23                                                                 T = 3.5 73 27                                                                 T = 4.0 71 29                                                                 T = 6.0 61 39                                                                 T = 8.0 52 48                                                               ______________________________________                                    

These results indicate that at normal body temperature, a 50% conversionof 1α-hydroxyprevitamin D₂ to 1α-hydroxyvitamin D₂ in vitro requiredapproximately eight hours. In vivo one would expect a similar rate ofconversion. These data indicate that thermal conversion at normal bodytemperature is sufficiently slow that most of the 1α-hydroxyprevitamin Dcompound is absorbed into the blood stream in the previtamin form andconversion to the activated vitamin D counterpart occurs principallyafter absorption from the intestine. This results in a greater sustainedblood level of activated vitamin D with less stimulation of intestinalcalcium absorption than is seen with administering the correspondingactivated vitamin D compound orally.

EXAMPLE 2

In vitro biological activity.

1,25-Dihydroxyprevitamin D₃ or 1,25-dihydroxyvitamin D₃ are incubatedwith the vitamin D receptor protein and tracer amounts of ³ H-1,25-(OH)₂D₂ under standard conditions for a competitive binding assay. The amountof 1,25-dihydroxyprevitamin D₃ and 1,25-dihydroxyvitamin D₃ competitoris varied between 1.25 pg and 1.25 ng. Concurrent with the incubationsfor binding a tube of 1,25-dihydroxyprevitamin D₃ is incubated at thesame temperature and for the same length of time and is analyzed by HPLCfor the amount of 1,25-dihydroxyprevitamin D₃ that has equilibrated tothe vitamin form. The level of binding of the 1,25-dihydroxyprevitaminD₃ form is then corrected for the amount of the vitamin form that hasbeen generated during the assay procedure.

These procedures show that the 1,25-dihydroxyprevitamin D₃ form has anaffinity for the receptor less than 0.1 the affinity of the1,25-dihydroxyvitamin D₃ form.

EXAMPLE 3

Acute hypercalcemia testing.

Male weanling rats are fed a vitamin D deficient diet containing normalCa (0.47%) and P (0.3%). After approximately 4-6 weeks on this diet, therats are separated into five groups and orally administered either1,25-dihydroxyvitamin D₃ (0.06 or 0.12 ug/kg/day) or1,25-dihydroxyprevitamin D₃ (0.06 or 0.12 ug/kg/day) in a vehicle suchas lactose, or the vehicle alone (control), for 3 days. All animals areexsanguinated 24 hours after the last dose and the blood is analyzed forserum calcium and serum phosphorus. The results demonstrate that dosingwith 1,25-dihydroxyvitamin D₃ causes a greater rise in serum calcium andserum phosphorus than comparable dosing with 1,25-dihydroxyprevitaminD₃.

EXAMPLE 4

Bioavailability testing.

Male weanling rats are fed a diet deficient in vitamin D and with normalcalcium (0.47%). After a period of four weeks has elapsed, the rats aredivided into two groups, and orally administered either1α,25-dihydroxyprevitamin D₃ (0.25 μg/kg) in a vehicle such as lactoseor the vehicle (control) alone. Four hours after administration, therats are killed and their blood level of 1α,25-dihydroxyvitamin D₃ ismeasured using a standard technique.

Following this procedure demonstrates that the blood level of1α,25-dihydroxyvitamin D₃ in rats that are administered1α,25-dihydroxyprevitamin D₃ is significantly elevated over the bloodlevel of control animals.

EXAMPLE 5

In vivo biological activity testing.

Male weanling rats are fed a vitamin D deficient diet containing normalCa (0.47%) and P (0.3%). After four weeks on this diet, the rats areseparated into two groups and orally administered 0.42 μg/kg1,25-dihydroxyprevitamin D₃ in a vehicle such as lactose or the vehiclealone (control) for each of 14 days. Eight hours after the last dose,the rats are killed and the blood calcium, blood phosphorus, and blood1,25-dihydroxyvitamin D₃ levels are measured.

This procedure demonstrates that the serum calcium, serum phosphorus andserum 1,25-dihydroxyvitamin D₃ levels are higher in the1,25-dihydroxyprevitamin D₃ dosed animals than in the control animals.

EXAMPLE 6

Pharmacokinetics testing.

Male weanling rats are fed a vitamin D deficient diet containing normalCa (0.47%) and P (0.3%). After four weeks on this diet, the rats areseparated into seventeen groups and orally administered either1,25-dihydroxyvitamin D₃ or 1,25-dihydroxyprevitamin D₃ in a vehiclesuch as lactose or the vehicle alone (control). One group is killed 8hours after dosing with the vehicle. Eight groups are orallyadministered a single dose of either 1,25-dihydroxyprevitamin D₃ or1,25-dihydroxyvitamin D₃ and killed at 2, 4, 6, 9, 12, 18, 24, and 48hours after dosing. The blood is collected and analyzed for1,25-dihydroxyvitamin D₃ levels.

These procedures demonstrate that dosing with 1,25-dihydroxyprevitaminD₃ results in 1,25-dihydroxyvitamin D₃ serum levels with a slower riseand longer duration than the 1,25-dihydroxyvitamin D₃ pharmacokineticsobserved after dosing with 1,25-dihydroxyvitamin D₃.

EXAMPLE 7

Treatment of osteoporosis.

A clinical study is conducted with postmenopausal osteoporoticoutpatients having ages between 55 and 75 years. The study involves upto 120 patients randomly divided into three treatment groups, andcontinues for 24 months. Two of the treatment groups receive constantdosages of orally administered 1α,25-dihydroxyprevitamin D₃ (u.i.d.; twodifferent dose levels above 0.5 μg/day) and the other group receives amatching placebo. All patients maintain a normal intake of dietarycalcium (500 to 800 mg/day) and refrain from using calcium supplements.Efficacy is evaluated by pretreatment and posttreatment comparisons ofthe patient groups with regard to (a) total body, radial, femoral,and/or spinal bone mineral density as determined by x-ray absorptiometry(DEXA), (b) bone biopsies of the iliac crest, and (c) determinations ofserum osteocalcin. Safety is evaluated by comparisons of urinaryhydroxyproline excretion, serum and urine calcium levels, creatinineclearance, blood urea nitrogen, and other routine determinations.

This study demonstrates that patients treated with orally administered1α,25-dihydroxyprevitamin D₃ exhibit significantly higher total body,radial, femoral, and/or spinal bone densities relative to patientstreated with placebo. The treated patients also exhibit significantelevations in serum osteocalcin. Bone biopsies from the treated patientsshow that 1α,25-dihydroxyprevitamin D₃ stimulates normal bone formation.The monitored safety parameters confirm an insignificant incidence ofhypercalcemia or hypercalciuria, or any other metabolic disturbance with1α,25-dihydroxyprevitamin D₃.

EXAMPLE 8

Prevention of osteoporosis.

A clinical study is conducted with healthy postmenopausal women havingages between 55 and 60 years. The study involves up to 80 patientsrandomly divided into two treatment groups, and continues for 12 to 24months. One treatment group receives a constant dosage of1α,25-dihydroxyprevitamin D₃ (u.i.d.; a dose level above 0.5 μg/day) andthe other receives a matching placebo. The study is conducted asindicated in Example 6 above.

This study demonstrates that patients treated with1α,25-dihydroxyprevitamin D₃ exhibit reduced losses in total body,radial, femoral, and/or spinal bone densities relative to baselinevalues. In contrast, patients treated with placebo show significantlosses in these parameters relative to baseline values. The monitoredsafety parameters confirm the safety of long-term1α,25-dihydroxyprevitamin D₃ administration at this dose level.

EXAMPLE 9

Prevention of hypocalcemia and bone loss in renal dialysis patients.

A 12-month double-blind placebo-controlled clinical trial is conductedwith 30 men and/or women with renal disease who are undergoing chronichemodialysis. All patients enter an 8-week control period during whichtime they receive a maintenance dose of vitamin D₃ (400 IU/day). Afterthis control period, the patients are randomized into two treatmentgroups: one group receives a constant dosage of1α,25-dihydroxyprevitamin D₄ (u.i.d., a dosage greater than 3.0 μg/day),and the other group receives a matching placebo. Both treatment groupsreceive a maintenance dosage of vitamin D₃, maintain a normal intake ofdietary calcium, and refrain from using calcium supplements. Efficacy isevaluated by pretreatment and posttreatment comparisons of the twopatient groups with regard to (a) direct measurements of intestinalcalcium absorption, (b) total body, radial, femoral, and/or spinal bonemineral density, and (c) determinations of serum calcium andosteocalcin. Safety is evaluated by regular monitoring of serum calcium.

Analysis of the clinical data shows that 1α,25-dihydroxyprevitamin D₄significantly increases serum osteocalcin levels and intestinal calciumabsorption, as determined by measurements using a single- ordouble-isotope technique. Patients treated with this compound shownormalized serum calcium levels, stable values for total body, radial,femoral, and/or spinal bone densities relative to baseline values. Incontrast, patients treated with placebo show frequent hypocalcemia,significant reductions in total body, radial, femoral, and/or spinalbone density. An insignificant incidence of hypercalcemia is observed inthe treated group.

EXAMPLE 10

Treatment of psoriasis.

An oral dosage formulation containing 1α,24-dihydroxyprevitamin D₂ isevaluated in a double blind study for therapeutic efficacy of theformulation in the treatment of dermatitis (contact and ectopic). Theformulation evaluated contains 1.0 to 2.0 μg of1α,24-dihydroxyprevitamin D₂. The control formulation is identicalexcept that it does not contain the 1α,24-dihydroxyprevitamin D₂. Thepatients are treated in an outpatient clinic and are divided into anexperimental and control population. They are instructed to take themedication once a day, in the morning before breakfast.

In each patient (experimental and control) an area of the skincontaining a lesion is selected which is ordinarily covered by clothingand the patients are instructed not to expose the skin area selected forstudy to sunlight. The area of the lesion is estimated and recorded, andthe lesion(s) is photographed. Relevant details of the photographicprocedure are recorded so as to be reproduced when the lesions are nextphotographed (distance, aperture, angle, background, etc.).

Evaluations of erythema, scaling, and thickness are conducted at weeklyintervals by a physician. The final evaluation is usually carried out atthe end of four to six weeks of treatment. The results of the study showthat daily oral administration of 1,24-dihydroxyprevitamin D₂significantly reduces the degree of erythema, scaling, and thicknessversus the control patients.

In summary, the present invention provides methods for amelioratingcertain medical conditions by improving blood levels of activatedvitamin D. The improved levels are achieved by administration of an oralformulation of 1α-hydroxyprevitamin D. The 1α-hydroxyprevitamin D is notactive in the intestine to stimulate calcium absorption, thus, reducingsignificantly the risk of hypercalcemia associated with known oralformulation of vitamin D. Conversion of the previtamin form to theactivated vitamin D occurs over time, primarily in the blood afterabsorption of the previtamin from the intestine, thus, producing higherlevels for a greater sustained time per administration.

While the present invention has now been described and exemplified withsome specificity, those skilled in the art will appreciate the variousmodifications, including variations, additions, and omissions, that maybe made in what has been described. Accordingly, it is intended thatthese modifications also be encompassed by the present invention andthat the scope of the present invention be limited solely by thebroadest interpretation that lawfully can be accorded the appendedclaims.

What is claimed is:
 1. A method for increasing the blood level ofactivated vitamin D in an animal or human in need thereof, comprisingthe step of administering orally to the animal or human an effectiveamount of substantially pure, solvent-free crystalline1α-hydroxyprevitamin D which is a 1α-hydroxyprevitamin D₂, a1α-hydroxyprevitamin D₃ or a 1α-hydroxyprevitamin D₄, in combinationwith a pharmaceutically acceptable excipient, the 1α-hydroxyprevitamin Dbeing stable at room temperature and substantially free of its thermalisomer.
 2. The method of claim 1, wherein the 1α-hydroxyprevitamin D isadministered in an amount sufficient to sustain the blood level ofcorresponding activated vitamin D for a period of time greater than fourhours after ingestion.
 3. The method of claim 2, wherein said1α-hydroxyprevitamin D is 1α,25-dihydroxyprevitamin D₂.
 4. The method ofclaim 2, wherein said 1α-hydroxyprevitamin D is1α,25-dihydroxyprevitamin D₄.
 5. The method of claim 1, wherein said1α-hydroxyprevitamin D is 1α,25-dihydroxyprevitamin D₂.
 6. The method ofclaim 1, wherein said 1α-hydroxyprevitamin D is1α,25-dihydroxyprevitamin D₄.
 7. The method of claim 1, wherein said1α-hydroxyprevitamin is 1α,24-dihydroxyprevitamin D₂.
 8. The method ofclaim 1, wherein said amount of 1α-hydroxyprevitamin D is in a unitdosage form sufficient to deliver about 0.1 μg/day to about 100 μg/day.9. The method of claim 1, wherein said amount produces less toxicitythan orally administering the same amount of the corresponding vitaminas measured by blood serum levels of calcium over time after ingestion.10. The method as claimed in claim 1, wherein said 1α-hydroxyprevitaminD is selected from the group consisting of 1α,24,25-(OH)₃ preD₃ ;1α(OH)preD₃ ; 1α,24-(OH)₂ preD₃ ; 1α,24-(OH)₂ -25-FpreD₃ ; 1α,25-(OH)₂preD₂ ; 1α,24,25(OH)₃ preD₂ ; 1α-(OH)preD₂ ; 1α,24-(OH)₂ preD₂ ;1α,24-(OH)₂ -25-FpreD₂ ; 1α,25-(OH)₂ preD₄ ; 1α,24,25-(OH)₃ preD₄ ;1α-(OH)preD₄ ; 1α,24-(OH)₂ preD₄ and 1α,24-(OH)₂ -25-FpreD₄.
 11. Amethod for providing bioavailability of activated vitamin D with lesshypercalcemia than with oral dosing of the activated vitamin D,comprising administering orally to a human or animal a therapeuticallyeffective amount of a solvent-free 1α-hydroxyprevitamin D compound whichis 1α,25-dihydroxyprevitamin D₃ or 1α,24-dihydroxyprevitamin D₂, whereinthe 1α-hydroxyprevitamin D compound is substantially pure, crystalline,stable at room temperature and substantially free of its thermal isomer.12. A method for reducing stimulation of intestinal calcium absorptionassociated with oral administration of vitamin D compounds, comprisingadministering orally to a human or animal a therapeutically effectiveamount of a solvent-free 1α-hydroxyprevitamin D compound which is1α,25-dihydroxyprevitamin D₃ or 1α,24-dihydroxyprevitamin D₂, said1α-hydroxyprevitamin D compound providing a bioavailable source ofactivated vitamin D, and said 1α-hydroxyprevitamin D compound being in aform which is substantially pure, crystalline, stable at roomtemperature and substantially free of its thermal isomer.
 13. A methodfor providing bioavailability of activated vitamin D with lesshypercalcemia than with oral dosing of the activated vitamin D,comprising administering orally to a human or animal a therapeuticallyeffective amount of a 1α-hydroxyprevitamin D compound which is a1α-hydroxyprevitamin D₂, a 1α-hydroxyprevitamin D₃ or a1α-hydroxyprevitamin D₄ in a form which is substantially pure,crystalline, substantially free of its thermal isomer, solvent-free andheat-stable at room temperature.
 14. The method of claim 13 wherein the1α-hydroxyprevitamin D compound is 1α,25-dihydroxyprevitamin D₂.
 15. Amethod for reducing stimulation of intestinal calcium absorptionassociated with oral administration of vitamin D compounds, comprisingadministering orally to a human or animal a therapeutically effectiveamount of a solvent-free 1α-hydroxyprevitamin D compound which is1α,25-dihydroxyprevitamin D₃, said 1α-hydroxyprevitamin D compoundproviding a bioavailable source of activated vitamin D, said1α-hydroxyprevitamin D compound being in a form which is substantiallypure, crystalline, stable at room temperature and substantially free ofits thermal isomer.